/*
 * Copyright 2018- The Pixie Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

// Copied from https://github.com/libarchive/libarchive/blob/master/examples/minitar/minitar.c

/*-
 * This file is in the public domain.
 * Do with it as you will.
 */

/*-
 * This is a compact "tar" program whose primary goal is small size.
 * Statically linked, it can be very small indeed.  This serves a number
 * of goals:
 *   o a testbed for libarchive (to check for link pollution),
 *   o a useful tool for space-constrained systems (boot floppies, etc),
 *   o a place to experiment with new implementation ideas for bsdtar,
 *   o a small program to demonstrate libarchive usage.
 *
 * Use the following macros to suppress features:
 *   NO_BZIP2 - Implies NO_BZIP2_CREATE and NO_BZIP2_EXTRACT
 *   NO_BZIP2_CREATE - Suppress bzip2 compression support.
 *   NO_BZIP2_EXTRACT - Suppress bzip2 auto-detection and decompression.
 *   NO_COMPRESS - Implies NO_COMPRESS_CREATE and NO_COMPRESS_EXTRACT
 *   NO_COMPRESS_CREATE - Suppress compress(1) compression support
 *   NO_COMPRESS_EXTRACT - Suppress compress(1) auto-detect and decompression.
 *   NO_CREATE - Suppress all archive creation support.
 *   NO_CPIO_EXTRACT - Suppress auto-detect and dearchiving of cpio archives.
 *   NO_GZIP - Implies NO_GZIP_CREATE and NO_GZIP_EXTRACT
 *   NO_GZIP_CREATE - Suppress gzip compression support.
 *   NO_GZIP_EXTRACT - Suppress gzip auto-detection and decompression.
 *   NO_LOOKUP - Try to avoid getpw/getgr routines, which can be very large
 *   NO_TAR_EXTRACT - Suppress tar extraction
 *
 * With all of the above macros defined (except NO_TAR_EXTRACT), you
 * get a very small program that can recognize and extract essentially
 * any uncompressed tar archive.  On FreeBSD 5.1, this minimal program
 * is under 64k, statically linked, which compares rather favorably to
 *         main(){printf("hello, world");}
 * which is over 60k statically linked on the same operating system.
 * Without any of the above macros, you get a static executable of
 * about 180k with a lot of very sophisticated modern features.
 * Obviously, it's trivial to add support for ISO, Zip, mtree,
 * lzma/xz, etc.  Just fill in the appropriate setup calls.
 */

#include <sys/stat.h>
#include <sys/types.h>

#include <archive.h>
#include <archive_entry.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
 * NO_CREATE implies NO_BZIP2_CREATE and NO_GZIP_CREATE and NO_COMPRESS_CREATE.
 */
#ifdef NO_CREATE
#undef NO_BZIP2_CREATE
#define NO_BZIP2_CREATE
#undef NO_COMPRESS_CREATE
#define NO_COMPRESS_CREATE
#undef NO_GZIP_CREATE
#define NO_GZIP_CREATE
#endif

/*
 * The combination of NO_BZIP2_CREATE and NO_BZIP2_EXTRACT is
 * equivalent to NO_BZIP2.
 */
#ifdef NO_BZIP2_CREATE
#ifdef NO_BZIP2_EXTRACT
#undef NO_BZIP2
#define NO_BZIP2
#endif
#endif

#ifdef NO_BZIP2
#undef NO_BZIP2_EXTRACT
#define NO_BZIP2_EXTRACT
#undef NO_BZIP2_CREATE
#define NO_BZIP2_CREATE
#endif

/*
 * The combination of NO_COMPRESS_CREATE and NO_COMPRESS_EXTRACT is
 * equivalent to NO_COMPRESS.
 */
#ifdef NO_COMPRESS_CREATE
#ifdef NO_COMPRESS_EXTRACT
#undef NO_COMPRESS
#define NO_COMPRESS
#endif
#endif

#ifdef NO_COMPRESS
#undef NO_COMPRESS_EXTRACT
#define NO_COMPRESS_EXTRACT
#undef NO_COMPRESS_CREATE
#define NO_COMPRESS_CREATE
#endif

/*
 * The combination of NO_GZIP_CREATE and NO_GZIP_EXTRACT is
 * equivalent to NO_GZIP.
 */
#ifdef NO_GZIP_CREATE
#ifdef NO_GZIP_EXTRACT
#undef NO_GZIP
#define NO_GZIP
#endif
#endif

#ifdef NO_GZIP
#undef NO_GZIP_EXTRACT
#define NO_GZIP_EXTRACT
#undef NO_GZIP_CREATE
#define NO_GZIP_CREATE
#endif

#ifndef NO_CREATE
static void create(const char* filename, int compress, const char** argv);
#endif
static void errmsg(const char*);
static void extract(const char* filename, int do_extract, int flags);
static int copy_data(struct archive*, struct archive*);
static void msg(const char*);
static void usage(void);

static int verbose = 0;

int main(int argc, const char** argv) {
  const char* filename = NULL;
  int compress, flags, mode, opt;

  (void)argc;
  mode = 'x';
  verbose = 0;
  compress = '\0';
  flags = ARCHIVE_EXTRACT_TIME;

  /* Among other sins, getopt(3) pulls in printf(3). */
  while (*++argv != NULL && **argv == '-') {
    const char* p = *argv + 1;

    while ((opt = *p++) != '\0') {
      switch (opt) {
#ifndef NO_CREATE
        case 'c':
          mode = opt;
          break;
#endif
        case 'f':
          if (*p != '\0')
            filename = p;
          else
            filename = *++argv;
          p += strlen(p);
          break;
#ifndef NO_BZIP2_CREATE
        case 'j':
          compress = opt;
          break;
#endif
        case 'p':
          flags |= ARCHIVE_EXTRACT_PERM;
          flags |= ARCHIVE_EXTRACT_ACL;
          flags |= ARCHIVE_EXTRACT_FFLAGS;
          break;
        case 't':
          mode = opt;
          break;
        case 'v':
          verbose++;
          break;
        case 'x':
          mode = opt;
          break;
#ifndef NO_BZIP2_CREATE
        case 'y':
          compress = opt;
          break;
#endif
#ifndef NO_COMPRESS_CREATE
        case 'Z':
          compress = opt;
          break;
#endif
#ifndef NO_GZIP_CREATE
        case 'z':
          compress = opt;
          break;
#endif
        default:
          usage();
      }
    }
  }

  switch (mode) {
#ifndef NO_CREATE
    case 'c':
      create(filename, compress, argv);
      break;
#endif
    case 't':
      extract(filename, 0, flags);
      break;
    case 'x':
      extract(filename, 1, flags);
      break;
  }

  return (0);
}

#ifndef NO_CREATE
static char buff[16384];

static void create(const char* filename, int compress, const char** argv) {
  struct archive* a;
  struct archive_entry* entry;
  ssize_t len;
  int fd;

  a = archive_write_new();
  switch (compress) {
#ifndef NO_BZIP2_CREATE
    case 'j':
    case 'y':
      archive_write_add_filter_bzip2(a);
      break;
#endif
#ifndef NO_COMPRESS_CREATE
    case 'Z':
      archive_write_add_filter_compress(a);
      break;
#endif
#ifndef NO_GZIP_CREATE
    case 'z':
      archive_write_add_filter_gzip(a);
      break;
#endif
    default:
      archive_write_add_filter_none(a);
      break;
  }
  archive_write_set_format_ustar(a);
  if (filename != NULL && strcmp(filename, "-") == 0) filename = NULL;
  archive_write_open_filename(a, filename);

  while (*argv != NULL) {
    struct archive* disk = archive_read_disk_new();
#ifndef NO_LOOKUP
    archive_read_disk_set_standard_lookup(disk);
#endif
    int r;

    r = archive_read_disk_open(disk, *argv);
    if (r != ARCHIVE_OK) {
      errmsg(archive_error_string(disk));
      errmsg("\n");
      exit(1);
    }

    for (;;) {
      int needcr = 0;

      entry = archive_entry_new();
      r = archive_read_next_header2(disk, entry);
      if (r == ARCHIVE_EOF) break;
      if (r != ARCHIVE_OK) {
        errmsg(archive_error_string(disk));
        errmsg("\n");
        exit(1);
      }
      archive_read_disk_descend(disk);
      if (verbose) {
        msg("a ");
        msg(archive_entry_pathname(entry));
        needcr = 1;
      }
      r = archive_write_header(a, entry);
      if (r < ARCHIVE_OK) {
        errmsg(": ");
        errmsg(archive_error_string(a));
        needcr = 1;
      }
      if (r == ARCHIVE_FATAL) exit(1);
      if (r > ARCHIVE_FAILED) {
#if 0
        /* Ideally, we would be able to use
         * the same code to copy a body from
         * an archive_read_disk to an
         * archive_write that we use for
         * copying data from an archive_read
         * to an archive_write_disk.
         * Unfortunately, this doesn't quite
         * work yet. */
            copy_data(disk, a);
#else
        /* For now, we use a simpler loop to copy data
         * into the target archive. */
        fd = open(archive_entry_sourcepath(entry), O_RDONLY);
        len = read(fd, buff, sizeof(buff));
        while (len > 0) {
          archive_write_data(a, buff, len);
          len = read(fd, buff, sizeof(buff));
        }
        close(fd);
#endif
      }
      archive_entry_free(entry);
      if (needcr) msg("\n");
    }
    archive_read_close(disk);
    archive_read_free(disk);
    argv++;
  }
  archive_write_close(a);
  archive_write_free(a);
}
#endif

static void extract(const char* filename, int do_extract, int flags) {
  struct archive* a;
  struct archive* ext;
  struct archive_entry* entry;
  int r;

  a = archive_read_new();
  ext = archive_write_disk_new();
  archive_write_disk_set_options(ext, flags);
#ifndef NO_BZIP2_EXTRACT
  archive_read_support_filter_bzip2(a);
#endif
#ifndef NO_GZIP_EXTRACT
  archive_read_support_filter_gzip(a);
#endif
#ifndef NO_COMPRESS_EXTRACT
  archive_read_support_filter_compress(a);
#endif
#ifndef NO_TAR_EXTRACT
  archive_read_support_format_tar(a);
#endif
#ifndef NO_CPIO_EXTRACT
  archive_read_support_format_cpio(a);
#endif
#ifndef NO_LOOKUP
  archive_write_disk_set_standard_lookup(ext);
#endif
  if (filename != NULL && strcmp(filename, "-") == 0) filename = NULL;
  if ((r = archive_read_open_filename(a, filename, 10240))) {
    errmsg(archive_error_string(a));
    errmsg("\n");
    exit(r);
  }
  for (;;) {
    int needcr = 0;
    r = archive_read_next_header(a, &entry);
    if (r == ARCHIVE_EOF) break;
    if (r != ARCHIVE_OK) {
      errmsg(archive_error_string(a));
      errmsg("\n");
      exit(1);
    }
    if (verbose && do_extract) msg("x ");
    if (verbose || !do_extract) {
      msg(archive_entry_pathname(entry));
      msg(" ");
      needcr = 1;
    }
    if (do_extract) {
      r = archive_write_header(ext, entry);
      if (r != ARCHIVE_OK) {
        errmsg(archive_error_string(a));
        needcr = 1;
      } else {
        r = copy_data(a, ext);
        if (r != ARCHIVE_OK) needcr = 1;
      }
    }
    if (needcr) msg("\n");
  }
  archive_read_close(a);
  archive_read_free(a);

  archive_write_close(ext);
  archive_write_free(ext);
  exit(0);
}

static int copy_data(struct archive* ar, struct archive* aw) {
  int r;
  const void* buff;
  size_t size;
  int64_t offset;

  for (;;) {
    r = archive_read_data_block(ar, &buff, &size, &offset);
    if (r == ARCHIVE_EOF) return (ARCHIVE_OK);
    if (r != ARCHIVE_OK) {
      errmsg(archive_error_string(ar));
      return (r);
    }
    r = archive_write_data_block(aw, buff, size, offset);
    if (r != ARCHIVE_OK) {
      errmsg(archive_error_string(ar));
      return (r);
    }
  }
}

static void msg(const char* m) { write(1, m, strlen(m)); }

static void errmsg(const char* m) {
  if (m == NULL) {
    m = "Error: No error description provided.\n";
  }
  write(2, m, strlen(m));
}

static void usage(void) {
  /* Many program options depend on compile options. */
  const char* m =
      "Usage: minitar [-"
#ifndef NO_CREATE
      "c"
#endif
#ifndef NO_BZIP2
      "j"
#endif
      "tvx"
#ifndef NO_BZIP2
      "y"
#endif
#ifndef NO_COMPRESS
      "Z"
#endif
#ifndef NO_GZIP
      "z"
#endif
      "] [-f file] [file]\n";

  errmsg(m);
  exit(1);
}
